(a) Field of the Invention
The present invention relates to a liquid crystal display (LCD) device having an improved backlight unit and, more particularly, to the improvement of the structure of the reflecting member in the backlight unit of the LCD device.
(b) Description of the Related Art
The LCD device has the advantages of smaller thickness and lightweight, and thus is used as a flat display panel in a variety of applications. The LCD device generally includes a display panel, a backlight unit for irradiating the display panel from the rear surface thereof and a housing for receiving therein the display panel and the backlight unit in one body so that the front screen of the display panel is exposed from a front opening of the housing.
FIG. 1 shows the peripheral part of a conventional LCD device, generally designated by numeral 10, which includes a display panel 12 for displaying images on the front screen thereof, a backlight unit 14 disposed at the rear of the display panel for irradiating the display panel 12 from the rear surface thereof, and a housing 16 for receiving therein the display panel 12 and the backlight unit 14 as a single unit.
Referring additionally to FIG. 2 showing the developed configuration of the LCD device of FIG. 1, the housing 16 includes a flat case 18, with a central opening, for receiving therein the backlight unit 14, and a cover 20 for covering the display panel 12 disposed in front of the backlight unit 14. The cover 20 is engaged with the flat case 18 by using an engagement structure so that the cover 20 thrust the display panel 12 toward the backlight unit 14 within the housing 16.
The cover 20 is formed as a metallic frame having an opening 21 for exposing the front screen of the display panel 12 and a side wall 20a having a front rim defining the opening 21. The cover 20 functions also as an electrostatic shield. The display panel 12 includes a polarizing plate 25 as a part thereof, and mounts thereon LCD drivers 22 and 24 at the peripheral area thereof.
The backlight unit 14 includes, as shown in FIG. 1, a light source or elongate lamp 34, an optical-conductive plate 26 having a light-emission front surface 26a and a light-reception side surface 26b adjacent to the elongate lamp 34, a reflection sheet 28 disposed at the rear of the light-conductive plate 26 for reflecting the light within the light-conductive plate 26 toward the light-emission front surface 26b thereof, and a laminated optical layer structure 33 on the front surface 26a of the light-conductive plate 26. The laminated optical layer structure 33 includes, consecutively as viewed from the light-conductive plate 26, a first optical diffusion sheet 30, a first lens sheet 32, a second lens sheet 32, and a second optical diffusion sheet 30.
The optical diffusion sheets 30 have a function for diffusing the light to uniformalize the brightness of the front screen of the display panel 26, whereas the lens sheets 32 have a function for focusing the light toward the front screen of the display panel 26.
The elongate lamp 34 of the backlight unit 14 has a cylindrical shape extending along the light-reception side surface 26b of the light-conductive plate 26 with a gap therebetween. The backlight unit 14 has a U-shaped reflecting member 36 made of a metal for encircling the lamp 34 together with the light-conductive plate 26. The front leg 36a of the reflecting member 36 abuts the first optical diffusion sheet 30 and the first lens sheet 32 on the light-emission surface 26a of the light-conductive plate 26. The rear leg 36b of the reflecting member 36 extends between the reflection sheet 28 and the inner bottom surface of the flat case 18.
As shown in FIG. 3 depicting a portion of FIG. 1, the engagement structure 39 for the flat case 18 and the display panel 12 includes an engagement hole 39a formed in the flat case 18 and a protrusion 39b formed on a molded chassis 40, which is sandwiched between the display panel 12 and the cover 20. The flat case 18 and the molded chassis 40 are coupled by the engagement structure 39 and bolts 38.
The molded chassis 40 is made of plastics and, as shown in FIG. 1, has a side wall 40a including a first portion 40c sandwiched between the display panel 12 and the cover 20 and a second portion 40d disposed in contact with the side wall 18a of the flat case 18 for encircling the backlight unit 14. The molded chassis 40 also has an extension 40b extending from the first portion 40c between the display panel 12 and the backlight unit 14 for buffering the thrust force acting therebetween.
The reflecting member 36 is thrust by the second portion 40d toward the light-conductive plate 26 so that the reflecting member 36 and the second portion 40c sandwich therebetween a low-voltage cable 42 for the lamp 34. The second optical diffusion sheet 30 and the second lens sheet 32 extend between the extension 40b of the molded chassis 40 and the reflecting member 36.
FIG. 4 shows a modified configuration of the elongate reflecting member 46 in the art, wherein the front leg 36a of the reflecting member 36 abuts the light-reception side surface 26b of the light-conductive plate 26.
For assembly of the LCD device of FIG. 1, the lamp 34 is first received in the reflecting member 36, which is then attached to the laminated body 44 including the reflection sheet 28 and the light-conductive plate 26, and the resultant components are held by the molded chassis 40 within the flat case 18.
Subsequently, the flat case 18 and the molded chassis 40 are fixed together by the bolts 38 and the engagement structure 39, followed by stacking thereon the optical layer structure 33 including the optical diffusion sheets 30 and the lens sheets 32. Thus, the backlight unit 14 is fabricated.
Thereafter, the display panel 12 mounting thereon the LCD drivers 22 and 24 is stacked onto the emission surface of the backlight unit 14, followed by disposing the cover 20 onto the display panel 12 and fixed to the flat case 18 by using the engagement and fixing mechanisms.
In the conventional LCD device as described above, there are some drawbacks to be removed.
First, the light-conductive plate 26 is liable to damages at the light-emission surface 26a or the light-receptions surface 26b when the reflecting member 36 receiving therein the lamp 34 is attached to the laminated body 44. This degrades the product throughput of the LCD device.
Second, the fabrication steps for the LCD device including the step of attaching the reflecting member 36 to the light-conductive plate 26 are complicated, and thus automated fabrication is difficult to achieve.
Third, the overall thickness of the LCD device is not satisfactorily small enough.
Fourth, the gap or space between the lamp 34 and the reflecting member 36 is not satisfactorily large enough. This limits the amount of emitted light from the lamp 34 to be reflected by the reflecting member 36 toward the light-reception surface 26b. 
In the conventional techniques, such as described in JP-A-10-162617, -7-49497, -6-347784 and UM-A-6-87937, the above drawbacks in the LCD device are not removed.
It is an object of the present invention to solve at least one of the drawbacks as recited above and thereby provide an LCD device having an improved structure in relation to the backlight unit.
The present invention provides, in one aspect thereof, a liquid crystal display (LCD) device including a display panel having a display screen at a font side thereof, a backlight unit disposed at a rear side of the display panel for irradiating the display panel at the rear side thereof, and a housing for holding the display panel and the backlight unit in one body, the backlight unit including a light-conductive plate having a light-emission front surface and a light-reception side surface, an elongate lamp extending along the light-reception side surface for emitting light at the light-reception side surface, a reflection sheet disposed at a rear side of the light-conductive plate and the elongate lamp for reflecting the light toward the light-emission surface, and an elongate reflecting member extending substantially parallel to the elongate lamp and formed as an L-shaped member as viewed along an extending direction of the reflecting member, the L-shaped member including a front flange portion disposed in front of the elongate lamp and a side flange portion normal to the front screen for reflecting light from the elongate lamp in association with the reflection sheet.
The LCD device of the first aspect of the present invention alleviates the first through third drawbacks of the conventional LCD device as recited above, due to the L-shaped configuration of the elongate reflecting member. More specifically, the absence of the rear flange portion or rear leg reduces the overall thickness of the LCD device, and also reduces the possibility of the damage on the light-conductive plate after attachment of the light-conductive plate onto the elongate reflecting member. This allows an automated assembly of the LCD device without degrading the throughput thereof.
The present invention also provides, in another aspect thereof, a liquid crystal display (LCD) device including a display panel having a display screen at a font side thereof, a backlight unit disposed at a rear side of the display panel for irradiating the display panel at the rear side thereof, and a housing for holding the display panel and the backlight unit in one body, the backlight unit including a light-conductive plate having a light-emission front surface and a light-reception side surface, an elongate lamp extending along the light-reception side surface for emitting light at the light-reception side surface, a reflection sheet disposed at a rear side of the light-conductive plate and the elongate lamp for reflecting the light toward the light-emission surface, and an elongate reflecting member for reflecting the light toward the light-reception side surface, the elongate reflecting member extending substantially parallel to the elongate lamp and formed as a U-shaped member as viewed along an extending direction of the reflecting member, the U-shaped member including a front leg disposed in front of the elongate lamp and a rear leg disposed at a rear side of the elongate lamp, the housing having a cutout for allowing the rear leg of the elongate reflecting member to be substantially flush with a rear surface of said housing.
The LCD device of the second aspect of the present invention alleviates the fourth drawback of the LCD device as recited above. More specifically, the cutout of the housing allows the space between the elongate lamp and the reflecting member to be enlarged without increasing the overall thickness of the LCD device.
The term xe2x80x9cU-shaped memberxe2x80x9d as used herein means that the U-shaped member has a pair of leg portions substantially parallel to each other and a bridge portion bridging both the leg portions together. The corners of the U-shaped member may be round or edged. The term xe2x80x9cL-shaped memberxe2x80x9d as used herein means that the L-shaped member has a pair of flange portions forming therebetween substantially a right angle. The corner may be round or edged.